Some 51% of 18 to 34-year-olds polled by Savanta ComRes said they pray at least once a month, compared with 24% of those aged 55 and over.
It also found 49% of the younger age group attend a place of worship every month, compared with 16% of over-55s.
The associate director of Savanta said the numbers could reflect the move to online worship during the pandemic.
Chris Hopkins added that there were "a few theories" as to why young people made up such a large proportion of the religious landscape.
"Firstly, as the demography of the UK changes, minority faiths do tend to have a larger proportion of practising young people, and therefore as the population of these groups increases within the UK, so will the prayer habits of the population at large," he said.
He explained it was important to "factor in the impact the pandemic has had on the ability to engage with one's faith" with virtual prayers and services being held online.
"It is possible that the pandemic opened up more avenues to prayer to young people, and this is reflected in the findings," he said.
The study polled 2,075 British adults in August and seems to contradict the stereotypical view that religious groups in the UK are overwhelmingly elderly.
A separate study by Manchester Metropolitan University coming out this week suggests religious communities have boomed in the pandemic with the move online.
Dr Alana Vincent, co-investigator of the British Ritual Innovation under Covid-19 (BRIC-19) project, said the pandemic "opened doors to those for whom worship has been inaccessible or uncomfortable".
She added: "Nevertheless, we've found that the actual experience of digital worship has been disappointing and frustrating for many people.
"This includes young adults, who in our survey have had a decidedly harder time than their older peers. Religious life can't escape the digital age, and it shouldn't - the need is real and significant."